Ophthalmic lens



H. H. STYLL.

OPHTHALMIC LENS.

APPLlCATlON FILED AUG. 23,

Patented Nov. 16, 1920.

F I GIII F I GIY INVENTOR H.H STYLL ATTORNEYS l3 I6. I

onl havin been ,tur'es hereinafter referred to, I

UNnsnsT TEs PATENT QFFICE.

HARRY H. STYLL, OF SOUTHBRIDGE, MASSACHUSETTS.

OPHTHALMIC LENS.

To all whom it may concern:

Be it known that I, HARRY H. STYLL, a

citizen of the 'United States, residing at southbridge in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Ophthalmic Lenses, of which the following is a specification. v V

This invention relates to ophthalmic lenses corrected to give substantially correct vision as regards both focus and astigmatism throughout the entire normal field of vision and is a division of my application filed June 23, 1919, Serial No. 306,117;

The principal object to-provide means to relate theopposite faces of the lensin such a way as to produce a minimum variation from the correct powers of focus and astigmatism of the lens at any one position within the normal 'field of vision.

Another object of this invention is to provide a way to reduce a large variation from the desired powers at any point or points within the normal field of vision :by introducing or adding permissible errorsat some other point or points within the normal field of vision so that the variations at all points within the normal field of vision will fall within a permissibleamount, that is to say, to producev a lens that while it may not be absolutely correct at any point, yet as a whole shall have no variations from correct powers that do not fall WI-H1111 a permissible' amount.

Other objects and advantages of themvention will be readily apparent by reference to the following specification taken in connection with the accompanying drawings, and it will be understood that Ima make any modifications in the'specific details of construction or steps'shown and described within the scope" of the appended claims without departing from or exceeding the spirit of my invention, the preferred form sake of illustration. v To facilitate an understandin of the fea- V hive-appended a sheet'of' drawings, illustrative'of the "Similar fei'ences throughout the cations and drawings refer'to similar Specification of Letters Patent.

tional view of this invention is 7 point is not shown and described for Patented Nov. 16, 1920. and. this application filed August Figure I represents aface or' front View of an ophthalmic lens. Y

II-II of Fig. I

Fig. III represents a diagrammatic secon line II-'II of Fig. I. I Fig.- IV, also represents a diagrammatic sectionalview on line II-'II of Fig. I.

The normalangle of human vision is about sixty degrees. The usual marginal errors or abberations encountered in ophthalmic Fig. II represents a sectional view on line lenses are those'of focus or spherical power and those of astigmatism or cylindrical power, and these abberations cause-errors in both magnification: and in displacement of the image of the object.

Lenses hitherto have been corrected'in the marginal portions bothfor spherical and cylindrical abberations, but in all such lenses the calculations have been made for a lens of correct central or vertex power; that is to say, the center was made to the desired power and the errors were corrected from this point out to the'margin of the lens, thereforebemg ncreasingly greater as they receded from the center toward the edge.

of the lens. This is best illustrated in Fig. V; where it will be noted the angle 16 l3'15 diverges from the central point/16. In this invention the central or vertex held'as a fixture; in fact there is no fixed point in the lens, but on the other hand the calculations are based on a point somewhere within the normal field of vision that will produce the'smallest variations possible at all points within the field. fact 'errorsmaybe introduced atpoints ofno error, or small error, to aid in re ducing down or averaging up greater errors at other points, so'that at 'no point' will the errors be greater than an amount permissible to vision.

point and departed as little as possible therefrom at other points, but in this in 'vention the idea is to get an average lens that as a whole gives better results because at no point is the error greatenough t'obe injurious to vision.

i This is best .shown by referring to the drawings. In FiggI are shown central, intermediate and marginal powers of focus and astigmatism, 3. indicates the central ,95 The old art lenses were correct at one V of only-one way,

7 every point 1n the field of vision,

' 10 and 9 811, Fig.

power of focus; 2 the intermediate power of focus; 3 the marginal power of focus; 1 the central astigmatism; 5 the. intermediate astigmatism, and 6 the marginal 'astigma tism.

It will be seen ments or powers we may adjust and position to give the nearest approach to the desired powers. By taking some intermediate position, such ceedboth ways in our adjustments-instead as in Fig.7IV. From 9 we can adjust toward both the margin and the center until we arrive at a position where the average departureis a minimum for whereas in Fig. IV we'can only proceed from the center '16 toward the marginal points 13 and 15, giving a much wider divergence at the marginthan'would be obtained in Fig. III,"

working to both sides of an intermediate point. The divergence of the angles 9-7 III, is considerably angle 16-43-15 of 16-13 is practically the distance 89 or 9--10.

less than that of the Fig. IV, as the distance double that of '7 While I' have "referred to selecting the point 9, since it is easiest to show diagrammatically the result desired or intended in this manner, itis to be understood that in the actual production of the lens what 'is done is to select not a'single point but a' line, preferably concentric with the center 1 of the lens, .or dot line 17 in FigI of the drawings and including the points 2 and 5 previously referred to. The calculations for the lens will ordinarily be made so that this line, preferably though not necessarily circular in form, will contain the several points in the lens of correct power, while the lens within and without'this line will vary but slightly from said correct power so that the variations from thecorrect power will at both sides be but slight. and will be less than the variations found to be present in types of centrally corrected lenses which attempts have hithertobeen made to produce, and the variatio'n will thus be kept 50,

termed permissible error or an error which, while measurableby scientific instruments or the like, is so slight as toremain unnoticed by the eye of the user of the lens. Having six elementswhich may be varied, adjustments with these may be made whereby an average lens of the lowest possible variation can be produced. No one of all the six elements is to be considered as fixed but they are to be left free to enter the resultant equation of minimum variation of the visual field as a whole.

The processes of making these lenses are the usual processes of making ordinary comthat here we have six eleas 9 in Fig. III, we can prothis line being shown as a dash below what may be tions are made in the same way, only using the intermediate line 17, Fig. I as a basis instead of the central point 16, Fig. IV as has hitherto been done.

The lenses also can be made individually to a prescription, each face being calculated for the particular prescription, or they may be made in series, wherein one face for several powers of lenses is a constant, and the other side a variable. blanks ground on the constant side may be sold to the dealer, and the dealer can put the second side on to get the required prescription.

When ground in series the power of the face curves is suitably markedon the lens or container, and a chart is furnished the dealer showing the curve of the second side to give the required prescription. Tools also for grinding the second side are prepared and sold to the dealer. Each tool is numbered and marked to indicate the curve of its face. These tools are the ordinary lap tools. The charts show the constant curves, the variable curves, and the tool numbers.

This lens when produced in the series method can be supplied the patient as quickly and practically and as cheaply as the old commercial uncorrected ones.

The amount of permissible variation may be fixed at any desired predetermined standard satisfactory to the oculist. The one usually us'ed, however, is that amount by which ophthalmic lenses vary from each other in the commercialseries. At some portions of the range this is one-eighth of a diopter; at others a quarter, and so on, even up to one whole. diopter in very strong curves, gradually increasing from the weak stronger curves; The amount, therefore, most practicable toselect would be that by which corresponding ophthalmic lenses vary I to the Y but by a less amount than the center and edge and having the center a and edge portions of substantially corresponding powers differing by a prescribed amount from the said line.

' 3. As an article ofmanufacture an oph thalmic lens having a line concentricwith the lens centerof'prescribed power and an inclosed central portion varying from the prescribed power by less than a predetermined amount.

4. An improved lens having front and rear curved faces, said faces being related averaged between the central inclosed and marginal surrounding 10 portions of the lens substantially as and for the purpose described.

In testimony whereof I have affixed my signature, in presence of a witness.

HARRY H. STYLL. Witness:

H. K. PARSONS. 

